Reporting from Baltimore — The saga of the Harbaugh brothers is really a tale of the tape.

A good 15 feet of tape.

"John came up with this thing where he put a piece of athletic tape across the floor of the room we shared," said Jim, whose San Francisco 49ers will play John's Ravens in Baltimore on Thursday. "He proclaimed that I wasn't allowed to come on his side of the tape, and he wasn't allowed to come on my side."

Jim agreed to the plan, only later to realize most of the prime items — a record player, radio, desk and alarm clock — were on his brother's side of the room. Jim had the closet where they kept their clothes and the bedroom door on his side, yet John was allowed to use those as necessary.

"So the deal was the deal," Jim said. "But there are those 10 or 12 defining moments in your life, and that was one of them. I learned a valuable lesson the hard way: You negotiate a good deal up front."

It isn't a piece of adhesive separating the Harbaughs now, but opposite coasts and NFL conferences, and each brother can argue his is the prime side of the room. The two will be on opposing sidelines in a Thanksgiving Day showdown marking the first time in NFL history brothers have squared off against each other as head coaches.

The 49ers, fresh off a 6-10 season, have done a U-turn in Jim's first season, have won eight in a row, and at 9-1 have a five-game lead in the NFC West. The Ravens beat Cincinnati last Sunday to improve to 7-3 and claim a share of first place in the AFC North with Pittsburgh — a team Baltimore has already swept.

"There's always a sibling rivalry, but that's only going to be Thursday night," said John, 48, who is 15 months older than Jim. "There really is no rivalry, at least on my end, and I think Jim feels the same way.

"When he would lose a game, that would really hurt. You'd feel really bad. That's your family. The only people I root for in football are friends and family. Who they coach for, I couldn't care less."

Making this an even more memorable moment for the Harbaughs is that Friday is the 50th wedding anniversary of their parents, Jack and Jackie, who plan to stop by M&T Bank Stadium for family pictures before the game but won't stick around to watch the game in person. They'll watch it at John's house.

"I can't see myself in the stadium, Jackie as well," Jack said by telephone. "The emotions that we have watching a game, we don't want to subject anyone to that. That's just going to be between us privately."

After years of practice, the couple has learned to watch football together. Mostly.

"She jumps up in front of the screen every once in a while and blocks it off, and I have to kind of remind her," Jack said. "The thing about Jackie is she really knows the game."

As well she should. She was a cornerstone of Team Harbaugh, handling all the moves and most of the kid-raising as the family zigzagged all over the country for Jack's jobs as a college football assistant. The family moved 16 times. Jackie and daughter Joani, the youngest Harbaugh, watched John go off to play defensive back at Miami of Ohio, and Jim head to Michigan, where he was a star quarterback for the Wolverines (and later spent 14 seasons playing for six NFL teams).

Not surprisingly, John and Jim were intensely competitive, whether it was who could throw a football over the gigantic pine tree in front of their home in Ann Arbor, Mich. — Jim accomplished that with a mighty heave — or whose turn it was to mow the big backyard.

"Our biggest fight was always over who cut the grass last," John recalled in his office at Ravens headquarters. "Dad made a deal and said, 'You're both cutting the grass.' The backyard was huge and there was a hill, and the frontyard was like the size of this room and flat. So we had to alternate. Well, Jim would always swear up and down that he was the last guy to do the backyard.

"It was total crap. Total crap. And he knew it was crap, and we'd fight about it."

Jim has a very different recollection.

"My dad let me run the mower when I was 6," he said. "I took great pride in mowing the grass. I would cut it in configurations of playing fields, like baseball diamonds. I'd cut football fields into the grass, then play on it for a while and then cut the rest of it. I loved mowing the grass.

"The truth is that my dad always let me mow the grass, and I always wanted to. When I was about 10, John wanted to mow the grass, but I wouldn't let him. Then my dad said I had to. John's not remembering the early years when I was the only one cutting it."

Then there was a time Jack sent his sons to the house of fellow Michigan assistant Bill McCartney, who later coached Colorado to a share of the national championship. McCartney had younger sons, and Jack thought his boys would be a good influence on them; mentors maybe.